rfmedic
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Posts posted by rfmedic
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It can be done, however the equipment and engineering required for a simple gmrs repeater is NOT worth the effort or energy if you could get the station/their engineer to agree to it.
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I don’t live in NY but am curious how repeater communications fair in the Big Apple. Given that many repeaters are on top of tall buildings and there are so many tall buildings, how well does a mobile rig or HT work when in between all those buildings?
Never tried so I don’t know.
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Its not too terrible at all depending on the repeater.
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The 462.700 is open in brooklyn with a Pl of 100.0 from the listing
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I'll 2nd the Open-700 repeater, it seems to cover very well. I think if we got more people in the area to jump on it, there could be a possibility of a nice community forming on the air.
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Negative, DXCC entities and sovereign nations are 2 different lists. Lookup current DXCC Entities for the complete 325 recognized entities. These include islands/territories that are controlled by major nations but are not geographically located in those nations - i.e. - Guam, Samoa, USVI, BVI, Easter Island...
My count of 300 is the total combined multipliers from all 6 bands. The main bands averaged 70 mults with 20m having 91.
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Adding the LPF is a waste. The LPF would be necessary if you were running a circulator on the output of the transmit radio to supress the harmonics generated by the magnetic core.
Put more effort into your antenna system. Heliax and a better antenna. Decibel DB404/408/420 or a Commander PD-201 or PD-455. Thats the weak part of your system from what you have described.
Finally browsing the forum. My day to day rf engineering workload here in Gotham has kept me too busy for the hobbyist side of things.
-RFMedic
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I've been running multiple 900mhz repeaters for years. It is a great band. Similar to 440mhz but with sharper nulls etc... The trick is finding clear input and output freqs...my machines are on odd splits because of that but since everyone is on commercial radios it doesnt matter.
Motorola GTX and MCS2000 are my preference.
KENWOOD TK-981 my other preference.
For at home base antennas comet makes a really well performing fiberglass vertical.
LMR-400 or better is damn near mandatory.
Thats my 2cents. FYI nyc based.
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Hopefully this straightens this out for you:
Fixed station: A fixed station, not open to public correspondence, operated by, and for the sole use of those agencies operating their own radio communication facilities in the Public Safety, Industrial, Land Transportation, Marine, or Aviation Radio Services.
Base Station - A station at a specified site authorized to communicate with mobile stations.
ENGLISH NOW:
50watts is your max Mobile, Base, or Repeater
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Alerts - OK
Full time audio - BAD
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What's confusing is I used to be able to talk for at least 30 minutes with out any problems and that was with an older, lower capacity battery. The issue seemed to show up after the two Motorola's were programmed this last time. We added some frequencies, checked the power output to a dummy load, and also checked the frequency alignment. Everything looked good. I'm wondering if the CDM 1550 LS+ series has an internal adjustable set point for the low voltage alarm? Maybe that inadvertently got changed to a higher voltage number. Does that sound reasonable?
I have also been considering what you are suggesting with a duel battery set up, more so for emergencies than just my convenience.
I would try switching out for another CDM1550. I would also watch my battery voltage. SOME of the CDMs have had that problem where once voltage hits 11.5VDC the VCOs start to unlock and you get the beeping. Try another CDM, check voltages, reseat power connections on battery, verify inline fuse. My initial thoughts.
-RF Medic
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99% of commercial mobile radios were designed around end users who made short transmissions in bursts - dispatchers, drivers, etc... They were never intended for the 50-75% duty cycle that the hobbyist/gmrs world utilizes them for without additional cooling. Hence why they run extremely hot if you are BSing for 20minutes or longer. The UHF CDM is intended to be run at 40watts in high power. Additional cooling such as a small fan on the heat sink would be a good idea depending on your talking habits. The reason the software allows you to program up to "48watts" is to adjust to 40watts without having to do an alignment/power calibration on the unit in the field. Depending on soft-pot settings sometimes "42" gives you 40 or "46" gives you 40 etc...
-RfMedic
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Sent you a PM
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If you want to play with more than just analog FM, come to the dark....i mean ham side.
-RfMedic
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Thank you for the welcome! I am still debating on getting my tech ticket as well.
The ham activity in the area is much busier than the GMRS machines. There are a couple of good gmrs repeaters in the staten island area though, just not very busy.
-RfMedic
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Welcome to gmrs!
-Rfmedic
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Myself and JohnE are the two big techies for the NYC area with wide coverage repeaters if you have any questions... Welcome to GMRS!
- Logan5, Funktionalav, mainehazmt and 1 other
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The 7/8 RFS cable is only .50 ft more than the 1/2" and it cuts the loss is half. I'm trying to determine why the 7/8 Commscope is $1.90 per foot more than the 7/8 RFS. Will it last significantly longer, does it transmit better......??? I have been doing a lot of research and some very experienced folks have suggested 7/8 heliax for UHF so that is why I'm steering this ship in that direction.
No, what is the total length of the feedline run from the inside of the repeater shed to the antenna? Under a 100FT length 7/8" heliax is overkill for your application. 1/2" LDF4-50A is more than adequate on UHF up to 90-100FT in length especially for what you want to do.
There is no discernible performance difference between the commscope and RFS cables - it is just 2 rival manufacturers splitting hairs that are unmeasurable without expensive sweep gear.
RfMedic
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Regular muffin fan is fine - depending on the quality of the fan you may need a filter cap on the DC fan (small chicklet across the +/-) to keep any buzz out of the audio if it arises. Also keep the power to the fan as close to the power supply as possible and routed away from the audio chain.
If you are going to make it thermostatically controlled, around 90-100F is a good turn on time especially for a mobile.
RfMedic
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Bill if you need any help with the MASTR 2 or any questions let me know. I ran several of those exact stations both ham and commercial (@ the full 200watts) and they do work well. However they are aging so hopefully you don't have any major issues to sort out. Repair is usually a piece of cake as long as the exciter and receiver decks are in good shape. The PA's are the most common failure point. Station PA is approximately 250-500mw drive for 75-100out and the upper 2 standalone PA's are around 25-35watts in for 100watts out each.
NYC Repeaters
in General Discussion
Posted
I usually monitor the .700 repeater that has a 100 pl. Seems to do alright in brooklyn queens and lower manhattan. Its listed as open for everyone... I usually catch someone on there from time to time